With continuing efforts to produce internal combustion engines with increased efficiency, pressures and temperatures have increased within the combustion chamber. These increases in pressure and temperature may require differing materials and construction methods for pistons.
Many pistons are assembled from a crown portion and a skirt portion. The crown is typically made of a cast or forged steel while the skirt is typically made of a lighter material, such as aluminum. Coupling the crown to the skirt may be accomplished in a variety of ways, including using the wrist pin attached to both the skirt and the crown while attached to the rod, friction welding, and threaded connections.